This invention relates to a rotor of a rotating machine which is an electric generator or an electric motor. More specifically, the invention relates to a rotor having shaft means mounted therein integrally, and having a plurality of permanent magnets and a plurality of magnetic members disposed therein; and also relates to a method for producing the rotor.
An example of a rotor constituting a rotating machine which is an electric generator or an electric motor includes a rotating shaft, a relatively thick-walled sleeve fitted to and mounted on the rotating shaft, permanent magnets and magnetic members arranged radially and circumferentially alternately on an outer peripheral portion of the sleeve, and a pair of side covers disposed on axially opposite side surfaces of the sleeve, each of the permanent magnets and each of the magnetic members and holding the sleeve, permanent magnets and magnetic members while sandwiching the sleeve, permanent magnets and magnetic members in an axial direction. The sleeve and the pair of side covers are each formed of a nonmagnetic material such as austenitic stainless steel or an aluminum alloy. Each of the magnetic members is composed of a laminate of metal plates comprising a magnetic material, for example, electromagnetic steel sheets.
The sleeve is keyed to the rotating shaft, and thereby coupled thereto integrally. On an outer peripheral surface of the sleeve, there are formed grooves spaced in a circumferential direction and extending in an axial direction. At a radially inward position, corresponding to each of the grooves, in each of the magnetic members comprising the laminate of electromagnetic steel sheets, there is formed a protrusion extending radially inwardly. Each of the magnetic members is disposed such that the magnetic member cannot make relative rotations relative to the sleeve coupled to the rotating shaft, because the protrusion of the magnetic member is fitted into the corresponding groove formed in the outer peripheral surface of the sleeve. Each of the magnetic members has a projection extending radially outwardly of each of the permanent magnets. In each of the projections, a flange portion extending circumferentially bilaterally outwardly is formed. In this condition, consider a state in which each of the magnetic members is disposed on the sleeve, and each of the permanent magnets is inserted into, and held in, a radial space formed in the circumferential direction of each of the magnetic members. In this state, a radially outward end of each of the permanent magnets is held by each of the flange portions opposed with spacing in the circumferential direction so that the permanent magnet will not escape radially outwardly. Between the pair of side covers, a plurality of through bolts are disposed in such a manner as to pass through one of the side covers, each of the magnetic members, and the other side cover. An end portion of each of the through bolts is clamped by a nut. As a result, each of the permanent magnets and magnetic members arranged on the outer peripheral portion of the sleeve coupled to the rotating shaft has the axially opposite side surfaces thereof squeezed between the pair of side covers, together with the sleeve, whereby the permanent magnets, magnetic members, and sleeve are connected together integrally with the rotating shaft. A radially outward end surface of each of the magnetic members is an arcuate surface of substantially the same shape. These radially outward end surfaces are positioned with spacing in the circumferential direction on a circular outer peripheral surface having the same axis center as the rotating shaft (i.e., the spacing formed between the adjacent flange portions opposed in the circumferential direction).
However, the foregoing conventional rotor is composed of many kinds of and a large number of components, such as the rotating shaft, the sleeve, the keys for coupling the rotating shaft and the sleeve, the plurality of permanent magnets, the plurality of magnetic members, the pair of side covers, and the plurality of through bolts and nuts. Besides, these varieties of many components have to be gathered and assembled. Consequently, the number of the components is large, and the man-hours for assembly are many. The assembly work is laborious and the burden on labor is heavy. A relatively long assembly time is required, boosting the manufacturing cost as a whole. In addition, the radially outward end surface of each of the permanent magnets is exposed to the outside from a spacing formed between the circumferentially opposed flange portions of the magnetic member, and thus is not completely sealed. Surface treatment for antioxidation is required at this site. In this respect as well, a cost increase cannot be avoided.
An object of the present invention is to provide a novel rotor of a rotating machine, whose structure is simple and whose components are small in number; and which can be manufactured at a lower cost than in the earlier technologies.
Another object of the invention is to provide a method for producing a novel rotor of a rotating machine, the method facilitating production, being capable of shortening the manufacturing time, and thus enabling production at a lower cost than in the earlier technologies.
Other objects and characteristics of the invention will become clear from the following description for explaining in detail embodiments of the rotor of a rotating machine constituted according to the invention, and a method for producing the rotor, with reference to the accompanying drawings.
According to an aspect of the invention, there is provided a rotor of a rotating machine, comprising:
a body portion having shaft means mounted therein substantially integrally, having a substantially circular outer peripheral surface and opposite side surfaces, and being formed of a nonmagnetic material; and
permanent magnets and magnetic members provided integrally with the body portion, and arranged radially and circumferentially alternately in intimate contact with each other, wherein:
each of the permanent magnets is completely embedded in the body portion; and
each of the magnetic members has only a radially outward end surface thereof exposed, and has other surfaces thereof embedded in the body portion.
Preferably, each of the magnetic members has a projection extending radially outwardly of each of the permanent magnets, a space portion is formed in the circumferential direction by the adjacent projections outwardly of a radially outward end surface of each of the permanent magnets, the body portion is disposed so as to fill the space portions, and a gap among radially inward side surfaces of each of the permanent magnets and each of the magnetic members and an outer peripheral surface of the shaft means, and so as to cover axially opposite side surfaces of each of the permanent magnets and each of the magnetic members to a predetermined thickness, and the exposed radially outward end surface of each of the magnetic members is substantially coplanar with the outer peripheral surface of the body portion.
Preferably, overhangs extending in circumferentially mutually approaching directions from circumferentially opposed side surfaces of adjacent magnetic members and being opposed with a circumferential gap therebetween are formed in radially outward edge portions of the adjacent magnetic members.
Also preferably, a segment of the body portion is disposed so as to fill the space portion defined by the radially outward end surface of each of the permanent magnets, side surfaces of the adjacent magnetic members circumferentially opposed to each other radially outwardly of the end surface, and opposed surfaces and radially inward side surfaces of circumferentially opposed overhangs; and the exposed radially outward end surfaces of the magnetic members are partitioned at equal intervals by the segments of the body portion disposed so as to fill the circumferential gaps between the opposed overhangs.
According to another aspect of the invention, there is provided a method for producing a rotor of a rotating machine, comprising:
inserting and holding a non-magnetized permanent magnet in each of slots formed in a magnetic material of a substantially cylindrical shape having a circular outer peripheral surface, the slots being circumferentially spaced from each other and arranged radially, and the slots having one end open radially inwardly and having the other end closed, with an arcuate bridge portion being left between the other end and the outer peripheral surface, each of the non-magnetized permanent magnet being inserted and held in the slot such that a space portion is left between the non-magnetized permanent magnet and the bridge portion;
then setting shaft means in alignment with an axis center of the magnetic material;
then filling a molten nonmagnetic material into a gap among the magnetic material, each of the non-magnetized permanent magnets, and the shaft means, and into each of the space portions, and also covering axially opposite side surfaces of the magnetic material and each of the non-magnetized permanent magnets to a predetermined thickness, thereby forming a body portion, and casting the shaft means, the magnetic material and each of the non-magnetized permanent magnets integrally into the body portion;
cooling the composite;
then cutting an outer peripheral surface of the body portion and the outer peripheral surface of the magnetic material about an axis center of the shaft means to cut off each of the bridge portions, thereby converting the magnetic material into magnetic members circumferentially separated from each other, and making a radially outward end surface of each of the magnetic members form an exposed surface from the body portion, and also positioning the exposed surface to be substantially coplanar with the outer peripheral surface of the body portion; and
then magnetizing each of the non-magnetized permanent magnets from the exposed surface of each of the magnetic members.
According to a further aspect of the invention, there is provided a method for producing a rotor of a rotating machine, comprising:
inserting and holding a non-magnetized permanent magnet in each of slots formed in a magnetic material of a substantially cylindrical shape having a circular outer peripheral surface, the slots being circumferentially spaced from each other and arranged radially, and the slots having one end open radially inwardly and having the other end closed, with a bridge portion being left between the other end and the outer peripheral surface, the bridge portion having a notch extending radially outwardly from a radially inward end surface thereof, each of the non-magnetized permanent magnets being inserted and held in the slot such that a space portion is left between the non-magnetized permanent magnet and the bridge portion;
then setting shaft means in alignment with an axis center of the magnetic material;
then filling a molten nonmagnetic material into a gap among the magnetic material, each of the non-magnetized permanent magnets, and the shaft means, and into each of the space portions, and also covering axially opposite side surfaces of the magnetic material and each of the non-magnetized permanent magnets to a predetermined thickness, thereby forming a body portion, and casting the shaft means, the magnetic material and each of the non-magnetized permanent magnets integrally into the body a portion;
cooling the composite;
then cutting an outer peripheral surface of the body portion and the outer peripheral surface of the magnetic material about an axis center of the shaft means so that the bridge portions will be circumferentially separated, with the nonmagnetic material filled into each of the notches as a boundary between the adjacent bridge portions, thereby converting the magnetic material into magnetic members circumferentially separated from each other, and making a radially outward end surface of each of the magnetic members form an exposed surface from the body portion, and also positioning the exposed surface to be substantially coplanar with the outer peripheral surface of the body portion; and
then magnetizing each of the non-magnetized permanent magnets from the exposed surface of each of the magnetic members.